Two Stories: Winter Solstice 2009: Facts on Shortest Day of the Year

[Ronald Mastrogiuseppe]

December 21 is a Solstice Day in 2009 The December solstice will occur at 17:47 (or 5.47pm) Coordinated Universal Time (UTC) on December 21, 2009.   It is also known as the winter solstice in the northern hemisphere and the summer solstice in the southern hemisphere due to the seasonal differences. Its date varies from December 20 to December 23 depending on the year in the Gregorian calendar. To find the December solstice date in other time zones or other years, please use the Seasons Calculator. The December Solstice Explained The December solstice occurs when the sun reaches its most southerly declination of -23.5 degrees. In other words, it is when the North Pole is tilted 23.5 degrees away from the sun. Depending on the Gregorian calendar, the December solstice occurs annually on a day between December 20 and December 23. On this date, all places above a latitude of 66.5 degrees north are now in darkness, while locations below a latitude of 66.5 degrees south receive 24 hours of daylight. The sun is directly overhead on the Tropic of Capricorn in the southern hemisphere during the December solstice. It also marks the longest day of the year in terms of daylight hours for those living south of the Tropic of Capricorn. Those living or travelling south from the Antarctic Circle towards the South Pole will see the midnight sun during this time of the year. On the contrary, for an observer in the northern hemisphere, the December solstice marks the day of the year with the least hours of daylight for those living north of the Tropic of Cancer. Those living or traveling north of the Arctic Circle towards the North Pole will not be able to see the sun during this time of the year. Illustration is not to scale The December solstice in the calendar December 20 and December 23 solstices occur less frequently than December 21 or December 22 solstices in the Gregorian calendar. The last December 23 solstice occurred in 1903 and will not occur again until the year 2303. A December 20 solstice has occurred very rarely, with the next one occurring in the year 2080. As with the June solstice, the December solstice’s varying dates are mainly due to the calendar system. The Gregorian calendar, which is used in most western countries, has 365 days in a year and 366 days in a leap year. However, the tropical year, which is the length of time the sun takes to return to the same position in the seasons cycle (as seen from earth), is different to the calendar year. The tropical year is approximately 365.242199 days but varies from year to year because of the influence of other planets. The exact orbital and daily rotational motion of the earth, such as the “wobble” in the earth's axis (precession), also contributes to the changing solstice dates. Over the course of history, many different schemes have been devised to determine the start of the year. Some are astronomical, beginning at the September or March equinox, or at the June or December solstice. Solstices are more readily observable either by observing when the midday shadow of a gnomon is longest (winter solstice in the northern hemisphere) or shortest (summer solstice in the northern hemisphere). The solstices can also be observed by noting the point of time when the sun rises or sets as far south as it does during the course of the year (winter in the northern hemisphere) or maximally north (summer in the northern hemisphere). December solstice in relation to seasons It is important to note that earth does not move at a constant speed in its elliptical orbit. Therefore the seasons are not of equal length: the times taken for the sun to move from the vernal equinox to the summer solstice, to the autumnal equinox, to the winter solstice, and back to the vernal equinox are roughly 92.8, 93.6, 89.8 and 89.0 days respectively. The consolation in the northern hemisphere is that spring and summer last longer than autumn and winter (when the December solstice occurs). The relative position of the earth's axis to the sun changes during the cycle of seasons. This phenomenon is the reason why the sun’s height above the horizon changes throughout the year. It is also responsible for the seasons through controlling the intensity and duration of sunlight received at various locations around the planet. Useful Tools To calculate the approximate time and date (according to Coordinated Universal Time) of the March equinox, as well as the June and December solstices and the September equinox, click on the Seasons Calculator. These dates mark the beginning of the four seasons of the year, which are spring, summer, autumn (or fall) and winter. It is important to note that the seasons in the northern hemisphere are opposite to those in the southern hemisphere. Find out more about the Seasons Calculator and links to useful tools, such as the Day and Night World Map, Moon Calculator, Moon Phase Calculator, and Sunrise Calculator. The World Clock can also be used to find sunrise and sunset times, as well as the current position of the sun in major cities around the world. Simply select any location that is available from the World Clock and the calculator will adjust the local time in that particular city. Solstice’s influence on cultures The December solstice has played an important role the lives of many people in ancient times. To this day, the world is still influenced by various traditions linked to the observance of the December solstice. Astronomy calculators Seasons Calculator Moon Calculator – find times for moonrise, moonset and more Moon Phase Calculator – Calculate Moon Phases for any year Sunrise Calculator – find times for sunrise, sunset and more Day and Night World Map – See which parts of the Earth are currently illuminated by the Sun More information December Solstice Customs and Traditions The March Equinox Explained Customs and Holidays around the March Equinox June Solstice June Solstice Customs and Traditions September Equinox September Equinox Customs and Holidays Calendar tools Calendar for 2009 Calendar Generator – Create a calendar for any year Duration Between Two Dates – Calculates number of days Related time zone tools The World Clock – current times around the world Time Zone Converter – If it is 3 pm in New York, what time is it in Sydney? Fixed Time Calculator – If it's 3 pm in New York, what time is it in the rest of the world?     Winter Solstice 2009: Facts on Shortest Day of the Year Brian Handwerk for National Geographic News Updated December 21, 2009   Today is the winter solstice and the first day of winter in the Northern Hemisphere. It's all due to Earth's tilt, which ensures that the shortest day of every year falls around December 21. But it's not all about astronomy. Since ancient times people have marked the winter solstice with countless cultural and religious traditions—it's no coincidence the modern holiday season surrounds the first day of winter. Solstice in Space: Astronomy of the First Day of Winter During the winter solstice the sun hugs closer to the horizon than at any other time during the year, yielding the least amount of daylight annually. On the bright side, the day after the winter solstice marks the beginning of lengthening days leading up to the summer solstice. "Solstice" is derived from the Latin phrase for "sun stands still." That's because—after months of growing shorter and lower since the summer solstice—the sun's arc through the sky appears to stabilize, with the sun seeming to rise and set in the same two places for several days. Then the arc begins growing longer and higher in the sky, reaching its peak at the summer solstice. The solstices occur twice a year (around December 21 and June 21), because Earth is tilted by an average of 23.5 degrees as it orbits the sun—the same phenomenon that drives the seasons. During the warmer half of the year in the Northern Hemisphere, the North Pole is tilted toward the sun. The northern winter solstice occurs when the "top" half of Earth is tilted away from the sun at its most extreme angle of the year. Being the shortest day of the year, the winter solstice is essentially the year's darkest day, but it's not the coldest. Because the oceans are slow to heat and cool, in December they still retain some warmth from summer, delaying the coldest of winter days for another month and a half. Similarly, summer doesn't hit its heat peak until August, a month or two after the summer solstice. Winter Solstice Marked Since Ancient Times Throughout history, humans have celebrated the winter solstice, often with an appreciative eye toward the return of summer sunlight. Massive prehistoric monuments such as Ireland's mysterious Newgrange tomb (video) are aligned to capture the light at the moment of the winter solstice sunrise. (Related: "Ancient Irish Tomb Big Draw at Winter Solstice.") Germanic peoples of Northern Europe honored the winter solstice with Yule festivals—the origin of the still-standing tradition of the long-burning Yule log. The Roman feast of Saturnalia, honoring the God Saturn, was a weeklong December feast that included the observance of the winter solstice. Romans also celebrated the lengthening of days following the solstice by paying homage to Mithra—an ancient Persian god of light. Many modern pagans attempt to observe the winter solstice in the traditional manner of the ancients. "There is a resurgent interest in more traditional religious groups that is often driven by ecological motives," said Harry Yeide, a professor of religion at George Washington University. "These people do celebrate the solstice itself." Pagans aren't alone in commemorating the winter solstice in modern times. In a number of U.S. cities a Watertown, Massachusetts-based production called The Christmas Revels honors the winter solstice with an annually changing menu of traditional music and dance from around the world. "Nearly every northern culture has some sort of individual way of celebrating that shortest day," said Revels artistic director Patrick Swanson. "It's a lot of fun for us to dig up the traditional dance and music and even the plays [honoring] that time of the year." Of course, as the name suggests, The Christmas Revels mix ancient winter solstice traditions with customs of the holiday that largely replaced winter solstice celebrations across much of the Northern Hemisphere—Christmas. Winter Solstice's Christmas Connection Scholars aren't exactly sure of the date of Jesus Christ's birthday, the first Christmas. "In the early years of the Christian church, the calendar was centered around Easter," George Washington University's Yeide said. "Nobody knows exactly where and when they began to think it suitable to celebrate Christ's birth as well as the Passion cycle"—the Crucifixion and resurrection depicted in the Bible. (Related: "Christmas Star Mystery Continues.") Eastern churches traditionally celebrate Christmas on January 6, a date known as Epiphany in the West. The winter date may have originally been chosen on the basis that Christ's conception and Crucifixion would have fallen during the same season—and a spring conception would have resulted in a winter birth. But Christmas soon became co-mingled with traditional observances of the first day of winter. "As the Christmas celebration moved west," Yeide said "the date that had traditionally been used to celebrate the winter solstice became sort of available for conversion to the observance of Christmas. In the Western church the December date became the date for Christmas." Early church leaders endeavored to attract pagans to Christianity by adding Christian meaning to existing winter solstice festivals. "This gave rise to an interesting play on words," Yeide said. "In several languages, not just in English, people have traditionally compared the rebirth of the sun with the birth of the son of God."   © 1996-2008 National Geographic Society. All rights reserved.   Ron Mastrogiuseppe, Director Crater Lake Institute http://www.craterlakeinstitute.com 541-810-3944